1. Field of the Invention
The present invention relates to an antenna-equipped portable electronic device that communicates with an external device.
2. Related Art
Flip type cellular (portable) telephones having a key-side body and a display-side body (composed, for example, of an LCD (liquid crystal display)) that can be folded together via a hinge mechanism have become mainstream devices. A main antenna for communication and conversation for this kind of cellular telephone device is disposed at an end portion of the key-side body or near a hinge mechanism that connects the key-side body and display-side body.
Here, if the main antenna 103 is built into an end portion of the key-side body (the end portion not linked by the hinge portion 104), the resonant frequency fc of the main antenna 103 will fluctuate when the key-side body 101 and display-side body 102 of the cellular telephone device 100 face each other (closed state) (see FIG. 14A) and when the key-side body 101 and display-side body 102 of the cellular telephone device 100 are exposed to the outside (opened state) (see FIG. 14B).
A reason for the fluctuation of resonant frequency fc of the main antenna 103 is that when the cellular telephone device 100 is in an opened state, the antenna is not adjacent to electronic components such as a microphone disposed in display-side body 102; however, when the cellular telephone device 100 is in a closed state, the main antenna 103 becomes adjacent to electronic components such as a microphone in the display-side body 102, so the C component (capacitive component) between the main antenna 103 and the electronic components fluctuates (increases).
Here, due to the resonant frequency fc being determined by Equation (3), when the C component fluctuates, the resonant frequency fc will also fluctuate.fc=½π√(LC)  (3)
In this way, if the resonant frequency fc fluctuates when the cellular telephone device 100 is open and closed, reception sensitivity will decrease. It should be noted that FIG. 15 shows a comparison of the return loss for the cellular telephone device 100 in the closed state and the return loss for the cellular telephone device 100 in the opened sate.
[Patent Publication 1] Japanese Unexamined Patent Application, First Publication No. 2000-138522